Assembly for taking up and compensating for torque-induced shocks

ABSTRACT

A torsion damping assembly which is installed between the crankshaft of the engine and the input element of the change-speed transmission in a motor vehicle has two coaxial flywheels one of which is driven by the crankshaft and the other of which can transmit torque to the transmission in response to engagement of a friction clutch. The transmission of torque between the two flywheels takes place by way of a damper and a slip clutch which latter is effective only within a selected range of possible angular movements of the two flywheels relative to each other.

CROSS-REFERENCE TO RELATED CASES

This application is a continuation of application Ser. No. 669,770 filedNov. 8, 1984, now abandoned.

The assembly of the present invention is similar to the assembly whichis disclosed in commonly owned copending patent application Ser. No.661,028 filed Oct. 15, 1984 by Paul Maucher for "Assembly for taking upand compensating for torque-induced shocks", in commonly owned copendingpatent application Ser. No. 885,875 filed July 15, 1986 by Wolfgang Reikfor "Assembly for compensating for fluctuations of torque which istransmitted by an internal combustion engine",

and in commonly owned copending patent application Ser. No. 669,658filed Nov. 8, 1984 by Oswald Friedmann for "Assembly for damping torsionbetween the engine and the transmission of a motor vehicle".

BACKGROUND OF THE INVENTION

The invention relates to improvements in assemblies which can beutilized to take up and to compensate for shocks which develop as aresult of fluctuations in the rotational speed of the output element ofan internal combustion engine. More particularly, the invention relatesto improvements in assemblies which can be used in motor vehiclesbetween the internal combustion engine and the input element of achange-speed transmission to blunt the effects of shocks which developas a result of fluctuations in the transfer of torque between the engineand the transmission. Still more particularly, the invention relates toimprovements in assemblies of the type wherein a first rotary unitreceives torque from the engine, a second rotary unit transmits torqueto the transmission, the two units are coaxial with and rotatable withinlimits relative to each other, and the means for transmitting torquebetween the two units comprises a damper of vibrations and of otherundesirable movements. As a rule, or at least in many instances, thedamper comprises resilient elements which act in the circumferentialdirection of the two units and one or more friction generating devices.

Assemblies of the just outlined character are disclosed, for example, inGerman Offenlegungsschrift No. 29 26 012. The damping action between thetwo rotary units which can turn within limits with reference to oneanother is provided by energy storing devices in the form of coilsprings and by a friction generating device which is installed tooperate in parallel with the coil springs. The coil springs offer aprogressively increasing resistance to further angular displacements ofthe two units with reference to each other from a starting or neutralposition. In other words, the coil springs (or at least some of the coilsprings) will yield in response to the exertion of a relatively smallforce when one of the units beings to move from the neutral position,and the resistance increases progressively as the angular displacementof the one unit relative to the other unit increases. The resistancewhich the friction generating device offers to rotation of the one unitrelative to the other unit remains at least substantially constant.

Assemblies embodying the just described damper are designed to operatein such a way that their critical fundamental frequency, namely thecritical RPM of the driven and driving parts, develops at a resonancewhich is below the ignition cycle frequency when the RPM of the engineis at a minimum value, namely the lowest RPM at which the engine isstill running. However, when an internal combustion engine is started orturned off, it frequently takes a rather long period of time duringwhich the RPM is within the critical range so that the vibrationamplitude of the two units which are rotatable relative to each otherincreases still further as a result of excitation within such range ofrotational speeds. The result is that the resilient elements of thedamper between the two units undergo maximum deformation and enablerotation limiting stops on the two units to move into actual contactwith each other. Under such circumstances, i.e., when the two stopsactually abut against each other, the damper is totally ineffective inthat it cannot compensate for or take up any shocks. Therefore, thevehicle which embodies such an assembly is vulnerable to shocks whichdevelop while the two stops are in actual contact with one another dueto the absence of any damping or shock absorbing action. This not onlyaffects the comfort of the occupant or occupants of the motor vehiclebut also generates pronounced noise. Still further, the shafts, bearingsand certain other parts of the engine and transmission in the motorvehicle are likely to undergo substantial damage.

OBJECTS AND SUMMARY OF THE INVENTION

An object of the invention is to provide a novel and improved torsiondamping assembly which is particularly effective during starting and/orstoppage of the engine in a motor vehicle.

Another object of the invention is to provide an assembly which canensure adequate damping of undesirable movements and/or forces duringeach and every stage of the operation of a motor vehicle and is alsohighly effective during those stages when the aforediscussed and otherconventional torsion damping assemblies are incapable of providing anadequate damping action.

A further object of the invention is to provide a simple, compact andinexpensive torsion damping assembly which can be incorporated inexisting motor vehicles in lieu of presently known assemblies as asuperior substitute therefor.

A further object of the invention is to provide a torsion dampingassembly which can be used to compensate for shocks and variations oftorque with a higher degree of efficiency, reliability andpredictability than heretofore known assemblies.

An additional object of the invention is to provide a novel and improvedmethod of damping vibrations and/or other undesirable movements betweentwo coaxial parts of a flywheel in a motor vehicle.

A further object of the invention is to provide a novel and improvedmode of establishing a torque transmitting connection between theinternal combustion engine and the change-speed transmission of a motorvehicle.

Still another object of the invention is to provide novel and improveddamper means for use in the above outlined assembly.

Another object of the invention is to provide novel and improvedflywheels for use in the torsion damping assembly of the above outlinedcharacter.

The invention resides in the provision of an assembly which serves totake up and compensate for torque-induced shocks, especially to take upand compensate for torque which is transmitted between the internalcombustion engine and the change-speed transmission of a motor vehicle.The improved assembly comprises coaxial first and second units which aremounted for limited angular movements with reference to each other. thefirst unit normally receives torque from the engine and the second unitserves to normally trnasmit torque to the input element of thechange-speed transmission. The assembly further comprises a damper whichis disposed between the two units and operates to yieldably resistangular movement of the two units relative to each other, and at leastone slip clutch which is interposed between the two units and includesopposing emans for yieldably resisting a predetermined stage of angularmovement of the two units with reference to each other. The damper cancomprise a plurality of coil springs or other suitable energy storingelements which act in the circumferential direction of the two unitsand/or one or more friction generating devices which are interposedbetween the two units and can be arranged to oppose each and everyincrement of angular movement of the two units with reference to oneanother. The damper and the slip clutch preferably operate in series(i.e., they become effective one after the other), and the slip clutchcan constitute a multi-stage slip clutch. To this end, the slip clutchcan comprise a plurality of stages each of which serves to offer adifferent resistance to rotation of the two units relative to each otherin different angular positions of such units relative to each other. Theopposing means of the slip clutch can comprise resilient means in theform of diaphragm springs, leaf springs, coil springs and/or acombination of two or more different types of springs. The resilientmeans can include one or more springs which are effective to opposerotation of the two units relative to each other in at least one endportion of the aforementioned stage of angular movement during which theslip clutch is effective.

The first and second units preferably comprise first and secondflywheels, and the damper as well as the slip clutch are installed toyieldably resist rotation of the flywheels with reference to each other.In accordance with one presently preferred embodiment, the slip clutchcomprises a first component which extends substantailly radiallyinwardly from one of the flywheels and a second component which extendssubstantially radially from a portion of the other flywheel. One of thecomponents has at least one tooth and the other component has a toothspace into which the tooth extends with a predetermined clearance, asconsidered in the circumferential direction of the two flywheels. Thetooth preferably extends radially inwardly into the space between tworadially outwardly extending teeth of the other component. The opposingmeans of such slip clutch preferably comprises friction generating meanswhich is interposed between the two components to oppose angularmovements of such components with reference to each other, as consideredin the circumferential direction of the two units, as soon as theclearance between the tooth of the one component and a tooth of theother component is reduced to zero. The friction generating means cancomprise at least one friction generating element which is non-rotatablyaffixed to one of the components and bears against the other component.The friction generating means preferably comprises two frictiongenerating elements which are non-rotatably affixed to one of thecomponents, which flank the other component, and which are urged againstthe other component. The opposing means can further comprise resilientmeans (e.g., one or more coil springs) which is or are provided in thetooth space at one or both sides of the tooth of the one component.

One component of the slip clutch can cooperate with or constitute theinput component of the damper and the output component of such dampercan comprise a pair of coaxial discs which are non-rotatably secured toeach other and to one of the flywheels.

In accordance with another embodiment, the opposing means of the slipclutch can comprise at least one lamination provided on the firstcomponent of the slip clutch, at least one lamination provided on thesecond component of the slip clutch and means (e.g., a diaphragm spring)for biasing the laminations against each other. For example, theopposing means can comprise at least one first lamination on one of thecomponents of the slip clutch, at least two second laminations providedon the other component of the slip clutch and flanking the firstlamination, and a diaphragm spring which biases the second laminationsagainst the respective sides of the first lamination. In order to obtaina multi-stage slip clutch, the second laminations can be mounted on theother component of the slip clutch with a different degree of play, asconsidered in the circumferential direction of the two units. Frictionbetween one of the second laminations and the first lamination can bedifferent from friction between the first lamination and the othersecond lamination; this can also influence the torque which the slipclutch can transmit between the flywheels of the two units.

In accordance with an additional embodiment of the invention, the slipclutch can comprise means for changing the resistance of the opposingmeans to angular movements of the two units relative to each other inresponse to changes in angular positions of the two components of theslip clutch relative to one another. The opposing means of such slipclutch can comprise two neighboring friction generating elements (orsimply two neighboring rings or washers without any pronounced frictiongenerating properties) and prestressed resilient means for biasing thetwo friction generating elements against each other. The means forchanging the resistance of such opposing means can comprise means forvarying the stress upon the resilient means in response to angularmovement of the two units relative to each other. Such varying means cancomprise cooperating cam and follower means provided on the two frictiongenerating elements. One of these friction generating elements sharesthe angular movements of one of the components and the other frictiongenerating element shares the movements of the other component of theslip clutch. The resilient means can comprise a diaphragm spring and thecam and follower means can be provided with ramps which are inclinedwith reference to a plane extending at right angles to the common axisof the two units.

As a rule, the two units are rotatable clockwise and counterclockwiserelative to each other from a neutral position in which the two frictiongenerating elements of the slip clutch also assume a neutral position.The arrangement is preferably such that the bias of the diaphragm springis increased irrespective of whether one of the friction generatingelements is rotated clockwise or counterclockwise with reference to theother friction generating element or vice versa.

The first unit can receive from the engine nominal torque of apredetermined magnitude, and the magnitude of torque which the slipclutch can transmit between the two flywheels is less (but can also bemore) than the predetermined magnitude. For example, the slip clutch cantransmit between 8 and 60 percent (preferably between 10 and 35 percent)of the predetermined torque. The magnitude of torque which istransmitted by the slip clutch can be between 5 and 50 percent(preferably between 7 and 30 percent) of the magnitude of torque whichis transmitted by the damper. On the other hand, the magnitude of torquewhich the damper can transmit preferably exceeds the magnitude ofnominal torque which the first unit receives from the engine.

The aforementioned stage of angular movement of the two units relativeto each other can be between 10 and 50 degrees, preferably between 15and 35 degrees.

The damper and the slip clutch jointly permit an angular movement of thetwo units relative to each other through a predetermined angle, and thetwo components of the slip clutch are preferably movable relative toeach other through an angle which is between 60 and 110 percent (mostpreferably between 80 and 90 percent) of the predetermined angle. Thetwo components of the slip clutch are preferably turnable relative toeach other through angles exceeding the maximum angle of clockwise orcounterclockwise rotation of one of the flywheels with reference to theother flywheel. Also, the extent of angular displacement of one flywheelwith reference to the other flywheel in a clockwise direction can exceedthe extent of angular displacement of such one flywheel in acounterclockwise direction, or vice versa.

In the presently preferred torsion damping assembly, the slip clutch isdesigned to start opposing rotation of the two units relative to eachother (either in a clockwise or in a counterclockwise direction) afterthe one or the other unit leaves its neutral or starting position.During such initial stage or stages of rotation of the two unitsrelative to each other, their mutual angular movements are yieldablyresisted by the damper, i.e., by the aforementioned resilient elementsof the damper and/or by the friction generating device or devices of thedamper.

The slip clutch can constitute a so-called load-responsive clutch whoseopposing means begins to frictionally resist (yieldably oppose) furtherrotation of the two units relative to each other after the two unitscomplete an angular movement from neutral position through a preselectedangle which may but need not be the same for rotation in a clockwise andin a counterclockwise direction. Alternatively or in addition tofrictional resistance, the slip clutch which constitutes aload-responsive clutch can include means for storing energy after thetwo units complete a predetermined angular movement in a clockwise or ina counterclockwise direction with reference to one another.

The novel features which are considered as characteristics of theinvention are set forth in particular in the appended claims. Theimproved torsion damping assembly itself, however, both as to itsconstruction and its mode of operation, together with additionalfeatures and advantages thereof, will be best understood upon perusal ofthe following detailed description of certain specific embodiments withreference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a fragmentary axial sectional view of a torsion dampingassembly with a slip clutch which embodies one form of the invention;

FIG. 2 is a fragmentary sectional view as seen in the direction ofarrows from the line II--II of FIG. 1;

FIG. 3 is a diagram showing the characteristic damping curve of theassembly which is shown in FIGS. 1 and 2;

FIG. 4 is a fragmentary elevational view of a second slip clutch;

FIG. 5 is a sectional view as seen in the direction of arrows from theline V--V of FIG. 4;

FIG. 6 is a fragmentary sectional view similar to that of FIGS. 1 or 5but showing a portion of a third slip clutch; and

FIG. 7 is a sectional view substantially as seen in the direction ofarrows from the line VII--VII of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIGS. 1 and 2, there is shown a torsion dampingassembly 1 which operates between an internal combustion engine 105 anda change-speed transmission 110 in a motor vehicle. The assembly 1comprises two coaxial units A and B the first of which includes acrankshaft 5 which is driven by the engine 105 and a first flywheel 3,and the second of which comprises a second flywheel 4 and a frictionclutch 7. The crankshaft 3 is separably affixed to the flywheel 5 by anannulus of bolts 6 or other suitable fasteners, and the housing or cover11 of the friction clutch 7 is affixed to the flywheel 4. When theclutch 7 is engaged, its clutch disc or plate 9 transmits torque to theinput element 10 of the transmission 110. The clutch 7 further comprisesa pressure plate 8 which normally bears against one of two frictionlinings 9a on the clutch disc 9 and urges the other lining 9a intotorque-receiving engagement with the flywheel 4. A diaphragm spring 12of the friction clutch 7 is tiltable between two seats 12a of the cover11 and normally bears against the peripheral portion of the clutch plate8 so that the internally splined hub 9b of the clutch disc 9 rotates theexternally splined portion of the input element 10. In order todisengage the clutch 7, i.e., to terminate the transmission of torquebetween the engine 105 and the transmission 110, the radially inwardlyextending prongs 12b of the diaphragm spring 12 must be moved in adirection to the left, as viewed in FIG. 1, in order to move theradially outermost portion of the diaphragm spring 12 in a directionaway from the flywheel 4. The latter and the flywheel 3 togetherconstitute a composite flywheel 2 of the improved torsion damping device1 and this device further comprises a damper 13 which is installedbetween and yieldably opposes rotation of the flywheels 3 and 4 relativeto each other. In accordance with a feature of the invention, the meansfor opposing rotation of the flywheels 3 and 4 (i.e., of the units A andB) relative to each other further comprises a slip clutch 14 which isdisposed radially outwardly of the damper 13. The damper 13 and the slipclutch 14 operate in series.

A system 15 of bearings is interposed between the flywheels 3 and 4. Inthe embodiment of FIGS. 1 and 2, the system 15 comprises twoantifriction ball bearings 16 and 17 which are disposed side by side, asconsidered in the axial direction of the flywheels 3 and 4, and whichare but need not be identical. The outer race 16a of the bearing 16 isinstalled in a centrally located recess 18 of the flywheel 3 and iscompelled to share the angular movements of the latter. The inner race17a of the bearing 17 surrounds and is non-rotatably mounted on acentrally located protuberance 19 of the flywheel 4. This protuberancecenters the smaller-diameter extension 10a of the input element 10 andcontains a friction bearing for the extension 10a. The inner race 16b ofthe bearing 16 is non-rotatably connected to the outer race 17b of thebearing 17 by a coupling element 20 which has a cylindrical portion 20asurrounded by and non-rotatably secured to the inner race 16b and anannular or bell-shaped portion 20b which surrounds and is non-rotatablysecured to the outer race 17b. The two portions 20a, 20b of the couplingelement 20 are disposed side by side, as considered in the axialdirection of the flywheels 3 and 4, and are integrally connected to eachother by a washer-like radially extending portion of the couplingelement 20.

In order to ensure that the races 16b, 17b will rotate with reference tothe associated races 16a, 17a even if the flywheels 3 and 4 performsmall or minute oscillatory (back and forth) angular movements relativeto each other, the assembly 1 of FIGS. 1 and 2 further comprises twomotion transmitting devices 21 and 22 the first of which acts betweenthe cylindrical portion 20a and the flywheel 3 and the second of whichacts between the flywheel 4 and the annular portion 20b of the clutchelement 20. The illustrated motion transmitting devices 21 and 22 actnot unlike freewheels and compel the clutch element 20, and hence theraces 16b and 17b, to rotate in a single direction with reference to theflywheels 3 and 4. The direction in which the motion transmitting device21 blocks rotation of the coupling element 20 relative to the flywheel 3is the same in which the motion transmitting device 22 blocks rotationof the coupling element 20 with reference to the flywheel 4. The motiontransmitting devices 21 and 22 ensure uniform wear upon the tracks ofthe races 16a, 16b, 17a, 17b as well as upon the spherical rollingelements of the bearings 16 and 17 by preventing the rollings elementsfrom simply oscillating back and forth when the nature of operation ofthe vehicle is such that the flywheels 3 and 4 turn back and forthrelative to each other at a high frequency but at a low or very lowamplitude (e.g., less than one degree).

The peripheral portion 23 of the flywheel 3 constitutes acircumferentially complete rim which surrounds a chamber 24 for themajority of parts of or the entire damper 13 and slip clutch 14. Thatend face (23a) of the rim 23 of the flywheel 3 which faces toward theflywheel 4 is adjacent to the input component 25 of the slip clutch 14,and such input component is affixed to the flywheel 3 by a set of bolts,screws or other suitable fastener means 26. The input component 24comprises radially extending sections 25a and 25b which are staggeredrelative to each other, as considered in the axial direction of theflywheels 3, 4, and are connected to each other by an axially extendingsection 25c located in the chamber 24. The radially innermost section25b of the input component 25 has one or more radially inwardlyextending teeth 27 (See particularly FIG. 2) each of which is disposedin a tooth space 28 of the output component 29 of the slip clutch 14.The tooth space 28 which is shown in FIG. 2 is machined into or isotherwise formed in the periphery (radially outermost portion) of theoutput component 29. The tooth 27 is received in the tooth space 28 witha certain amount of play (30+30a) which determines the extent to whichthe components 25 and 29 of the slip clutch 14 are rotatably relative toeach other in the directions which are indicated by the arrows 44 and45. In FIG. 2, the component 25 is located in an intermediate positionbecause the play 30+30a has two portions disposed at the opposite sidesof the tooth 27. The flanks of the tooth 27 are denoted by the referencecharacters 27a and 27b; such flanks face helical springs 52 which arerecessed into the tooth flanks 28a, 28b of the component 29 and extendin part into the adjacent portions of the tooth space 28 at therespective sides of the tooth 27. The springs 52 are partially recessedinto the flanks 28a, 28b of teeth 29a and 29b which form part of thecomponent 29 and flank the tooth space 28.

The means for establishing a yieldable connection between the components24 and 29 of the slip clutch 14 comprises two friction generatingelements 31 and 31a which flank the components 24, 29 and are rigidly(non-rotatably) connected to the component 29. The connecting meanscomprises specially designed rivets 32 which are affixed to the radiallyoutermost portion of the component 29 of the slip clutch 14. Thefriction generating element 31a is movable axially of the flywheels 3, 4toward and away from the element 31 by sliding along the larger-diameterportions 33 of the rivets 32. The element 31a is or acts not unlike adiaphragm spring which reacts against the heads 32a of the rivets 32 andbears against the radially extending section 25b of the component 25.The element 31 is in frictional engagement with the corresponding sidesof both components (25, 29) of the slip clutch 14. It will be noted thatthe rivets 32 constitute retainers for the element or diaphragm spring31a as well as a means for holding the elements 31 and 31a againstrotation with reference to the components 25, 29. The element 31 is heldin requisite frictional engagement with the adjacent sides of thecomponents 25, 29 under the action of the prestressed diaphragm spring31a.

In the embodiment of FIGS. 1 and 2, the components 25, 29 and theelements 31, 31a are made of steel so that the frictional engagement isa metal-to-metal type engagement. However, it is equally possible toresort to organic or inorganic washers or like inserts (for example,between the metallic element 31 and the adjacent side of the section 25bof the component 25) in order to generate a different type of friction.

In accordance with a feature of the invention, the slip clutch 14 isintegrated into the damper 13. Thus, the radially innermost portion 34of the component 29 of the clutch 14 constitutes the input component ofthe damper 13 and is flanked by two spaced-apart discs 35, 36 formingpart of the unit B. The discs 35, 36 are rigidly connected to each otherand to the flywheel 4 by a set of distancing elements 37 in the form ofrivets whose central portions are received with play (as considered inthe circumferential direction of the flywheels 3 and 4) in arcuateslot-shaped openings 34b of the portion 34. The latter has windows 34awhich are flanked by windows 35a and 36a of the respective discs 35 and36. Each of the windows 34a receives a portion of a coil spring 38 whichconstitutes one energy storing element of the damper 13 and furtherextends into the respective windows 35a and 36a. The coil springs 38oppose rotation of the flywheels 3 and 4 relative to each other.

The damper 13 further comprises a friction generating device 39 whichyieldably opposes rotation of the flywheels 3 and 4 during each stage oftheir angular movement relative to one another, i.e., during each andevery stage of rotation of the discs 35, 36 relative to the innermostportion 34 of the output component 20 and/or vice versa. Still further,the damper 13 comprises an additional friction generating device 40which becomes effective only during a certain stage of angular movementof the flywheel 4 relative to the flywheel 3 in a clockwise orcounterclockwise direction, or vice versa.

The friction generating device 39 comprises a ring-shaped frictiongenerating element 39a which is interposed between the portion 34 andthe disc 36. Furthermore, the friction generating device 39 comprises adiaphragm spring 39b which reacts against the disc 35 and bears againstthe portion 34 so as to urge the latter into requisite frictionalengagement with the element 39a as well as to urge the element 39a intofrictional engagement with the disc 36.

The load-responsive friction generating device 40 comprises a frictionring 41 having axially extending arms 41a. The arms 41a extend axiallyfrom the radially innermost portion of the ring 41 and through aperturesor slots 42 of the portion 34. The apertures 42 merge into theaforementioned windows 34a of the portion 34 for the coil springs 38.The length of the apertures 42, as considered in the circumferentialdirection of the flywheels 3 and 4, is selected in such a way that theparts 41 and 34 can rotate relative to each other only during certainstages of angular movement of the flywheels 3 and 4 with reference toeach other. The device 40 further comprises a diaphragm spring 43 whoseradially outermost portion reacts against the radially outermost portionof the disc 35 and whose radially innermost portion bears against thetips of the arms 41a so that the radially outermost portion of the ring41 is maintained in frictional engagement with the adjacent side of thedisc 36. The discs 35 and 36 constitute the output component of thedamper 13 and determine the extent to which the portion 34 (i.e., theinput component of the damper 13) can turn with reference to theflywheel 4. As mentioned above, the discs 35 and 36 form part of theunit B because they are rigidly affixed to the flywheel 4. On the otherhand, the portion 34 is rigidly affixed to the flywheel 3 by thefastener means 26. The flywheels 3, 4 cannot turn relative to each otherwhen the central portions of the rivets 37 come into abutment with thesurfaces at the one or the other end of the respective arcuate slots 34bin the portion 34.

The dimensions of the windows 35a, 36a in the discs 35, 36, thedimensions of the windows 34a in the portion 34 of the output component29, and the dimensions and characteristics of the coil springs 38 areselected in such a way that the characteristic damping curve of theassembly 1 is a stepped curve, e.g., of the type shown in the diagram ofFIG. 3. In this diagram, the extent of angular displacement of theflywheels 3, 4 relative to each other is measured along the abscissa andthe magnitude of torque which is being transmitted between the twoflywheels is measured along the ordinate. The arrow 44 indicates thedirection in which the flywheel 3 rotates in order to drive the wheelsof the motor vehicle through the medium of the change-speed transmission110, and the arrow 45 indicates the direction of rotation when thevehicle is coating, i.e., when the output element 10 tends to transmittorque to the crankshaft 5.

It is assumed that the damper 12 is idle (its parts then assume thepositions which are shown in FIG. 1) and that the tooth 27 of the inputelement 25 of the slip clutch 14 is located in the central or neutralposition of FIG. 2. In such position, the tooth 27 may but need not belocated exactly midway between the flanks 28a, 28b of the neighboringteeth 29a and 29b on the output component 29 of the slip clutch 14. Ifthe flywheel 3 or 4 thereupon begins to turn relative to the flywheel 4or 3 in the direction or arrow 44, such angular movement is opposed atfirst by one or more coil springs 38 which constitute the first orweakest constitutents of the resilient means including all of the coilsprings 38 of the damper 13. When the flywheel 3 or 4 (let it be assumedhere that the flywheel 3 rotates relative to the flywheel 4) completesan angular movement through the angle A' (FIG. 3) and continues to turnin the direction of arrow 44, the weakest coil spring or springs 38 ofthe damper 13 are assisted by the next set of (stronger) coils springs38 so that the damper 13 then offers a more pronounced resistance torotation of the flywheel 3 relative to the flywheel 4. When the flywheel3 completes an angular movement through the angles A' and B', the coilsprings 38 of the first two sets of such springs in the damper 13jointly transmit a torque which matches the torque 46 that can betransmitted by the slip clutch 14. This, if the flywheel 3 continues toturn with reference to the flywheel 4 in the direction of arrow 44beyond the angle A'+B', the components 25, 29 of the slip clutch 14 moverelative to each other until the flank 27b of the tooth 27 shown in FIG.2 engages with the flank 28b of the tooth 29b on the component 29. Thisterminates the ability of the input and output components 25, 29 of theslip clutch 14 to move relative to each other. As the flywheel 3continues to turn in the direction of arrow 44 through the angle C ofFIG. 3, the components 25 and 29 rotate as a unit because the tooth 27of FIG. 2 continues to bear against the tooth 29b. When the angularmovement of the flywheel 3 through the angle A'+B'+C is completed, thecoil springs 38 of the first two sets undergo additional compressionwhile the flywheel 3 turns through the angle D. The coil spring orsprings 38 of the third set of such coil springs in the damper 13 storeenergy while the flywheel 3 turns through the angle E, i.e., rotation ofthe flywheel 3 relative to the flywheel 4 in the direction of arrow 44is then opposed by three sets of coil springs 38. Deformation of (i.e.,storing of energy by) the third set of coil springs 38 is terminatedwhen the flywheel 3 completes the angle A'+B'+C+D+E; at such time, themedian portions of the distancing elements 37 come into engagement withthe arcuate (concave) end portions of surfaces bounding the respectivearcuate slots 34b in the portion 34 of the output component 29 of theslip clutch 14. From there on, the flywheels 3 and 4 rotate as a unit ifthe flywheel 3 continues to turn in the direction of arrow 44. Thetorque which the damper 13 then transmits between the flywheels 3 and 4is shown in FIG. 3 at 47. Such torque preferably somewhat exceeds thenominal torque which is transmitted by the internal combustion engine105 so that the distancing elements 37 are likely to strike against theaforementioned arcuate and portions of surfaces bounding the respectiveslots 34b of the portion 34 (input component of the damper 13) only whenthe direction of load changes and the magnitude of transmitted torqueexceeds the anticipated magnitude.

During return movement of the parts of the damper 13 to their normal orstarting positions of FIG. 1 (such starting positions have been shiftedin the direction of arrow 44 through the angle C due to angular movementof the components 25, 29 of the slip clutch 14 relative to each otherand are indicated in FIG. 3 by the reference character 48), the coilsprings 38 of the damper 13 dissipate energy during an angular movementof the flywheel 3 relative to the flywheel 4 in the direction of arrow45 through an angle F. The angle F equals the sum of angles A', B', Dand E. The angle B'+D is the angle which is covered by the flywheel 3while the coil spring or coil springs 38 of the second set of suchsprings in the damper 13 dissipate energy. If the flywheel 3 continuesto turn relative to the flywheel 4 in the direction of arrow 45 beyondthe new neutral or starting position 48, the coil spring or coil springs38 of the first set being to store energy while the flywheel 3 turnsthrough an angle G. When the angular movement through the angle G (inthe direction of arrow 45) is completed, the parts 34 and 35, 36cooperate to stress the coil spring or coil springs 38 of the second setso that the angular movement of the flywheel 3 in the direction of arrow45 is then opposed by two sets of coil springs 38. Such springs continueto store energy until the torque which is generated thereby reaches thatvalue at which the coil springs of the first and second sets overcomethe force (46a) with which the components 25 and 29 of the slip clutch14 oppose rotation relative to each other. At such time, the components25 and 29 of the clutch 14 start to turn with reference to one anotherand this angular movement of the parts 25, 29 relative to one another isterminated when the flanks 27a of the teeth 27 on the input component 25engage the flanks 28a of the respective teeth 29a on the outputcomponent 29 of the slip clutch 14. Such angular movement of thecomponents 25, 29 of the slip clutch 14 relative to each other iscompleted while the flywheel 3 turns in the direction of arrow 45through an angle I. The reference character H denotes in FIG. 3 thatangle which is covered by the flywheel 3 in the direction of arrow 45while the coil spring or coil springs 38 of the second set of suchsprings in the damper 13 undergo additional compression before thecomponents 25, 29 of the slip clutch 14 begin to slide relative to eachother.

When the flanks 27a of the teeth 27 engage the flanks 28a of therespective teeth 29a on the output component 29 of the slip clutch 14,and if the flywheel 3 continues to turn in the direction of arrow 45,the coil spring or coil springs 38 of the second set of such springs inthe damper 13 undergo additional compression while the flywheel 3 turnsthrough an additional angle K, and such additional compression of thesecond set of coil springs is terminated when the distancing elements 37strike the respective end portions of surfaces bounding thecorresponding arcuate slots 34b in the input element 34 of the damper13. The magnitude of torque which is transmitted by the damper 13 atsuch time is shown at 49 in the right-hand portion of FIG. 3.

If the direction of rotation of the flywheel 3 relative to the flywheel4 is thereupon reversed (from the direction of the arrow 45 to thedirection of arrow 44), the coil springs 38 of the damper 13 dissipateenergy while the flywheel 3 turns throuh an angle L at which time theparts of the damper 13 reassume their starting or neutral positions(indicated by the reference character 50). Such neutral positions areshifted from the neutral positions denoted by the character 48 of FIG. 3by the angle I, i.e., an angle corresponding to that which is covered bythe flywheel 3 in the direction of arrow 45 while the components 25 and29 of the slip clutch 14 move relative to one another. the components25, 29 of the slips clutch 14 agains begin to move relative to eachother at the point 51 in the diagram of FIG. 3.

As can be seen in FIG. 3, the torque 47 (when the angular movement ofthe flywheel 3 relative to the flywheel 4 in the direction of arrow 44is terminated by the distancing elements 37 and the surfaces boundingthe respective slots 34b) exceeds the torque 49 which is transmitted bythe flywheel 3 when the latter completes its angular movement relativeto the flywheel 4 in the direction of arrow 45. In the illustratedembodiment, the torque 46 at which the clutch 14 begins to slip equalsor approximates 20% of the maximum torque 47 which the damper 13 cantransmit in the direction of arrow 44.

FIG. 3 further shows that the angle I (during which the components 25,29 of the slip clurch 14 turn relative to each other) exceeds the angleF or L, i.e., the angle through which the input and output components 34and 35, 36 of the damper 13 can turn relative to each other in thedirections of arrows 44 and 45, respectively. In the embodiment of FIGS.1 and 2, the angle L is smaller than the angle F, i.e., the anglethrough which the flywheel 3 turns relative to the flywheel 4 in thedirection of arrow 44 while the components 34 and 35, 36 of the damper13 turn relative to each other is greater than the angle which iscovered by the flywheel 3 in the direction of arrow 45 while thecomponents 34 and 35, 36 of the damper 13 turn relative to each other.

FIG. 3 does not shown the frictional hysteresis which is caused by thefriction generating devices 39 and 40 of the damper 13. The momentswhich are generated by the devices 39 and 40 are superimposed upon themoments which are generated by the coil springs 38 of the damper 13 isin those regions (i.e., during movement of the flywheel 3 relative tothe flywheel 4 through those angles) in which the devices 39 and 40 areoperative.

The coil springs 52 of FIG. 2 are optional. Such springs need notnecessarily be mounted on the teeth 29a, 29b of the output component 29of the slip clutch 14. For example, the springs 52 can be mounted on theteeth 27 or one thereof can be mounted on the tooth 27 while the otherspring 52 is mounted on the corresponding tooth 29a or 29b. The purposeof the springs 42 is to prevent the teeth 27, 29a or 27, 29b fromstriking against each other with a pronounced force. The effect of thesprings 52 is not shown in the diagram of FIG. 3. The resistance whichthe springs 52 offer to certain stages of further rotation of thecomponents 25 and 29 relative to each other is superimposed upon theslip torque of the clutch 14.

An advantage of the assembly 1 is that its constituents can be puttogether or taken apart in a simple and time saving manner. Thus, theflywheel 3 can be affixed to the crankshaft 5 by bolts 6 in a firststep, and the thus assembled unit A is then connected with thepreassembled unit B as well as with certain other parts by the fastenermeans 26. The flywheel 4 can be readily assembled with the damper 13,slip clutch 14 and friction clutch 7 preparatory to attachment to theflywheel 3 by fastener means 26. The clutch disc 9 is then alreadycentered between the pressure plate 8 of the friction clutch 7 and theflywheel 4. The system 15 of bearings 16 and 17 can be mounted on theflywheel 3 before the latter is connected with the flatwheel 4 byfastener means 26. Alternatively, the system 15 can be assembled withthe flywheel 4 before the latter is attached to the flywheel 3.

It has been found that, by the simple expedient of conforming the slipclutch 14 to the vibration characteristics of the engine 105 (primemover) and to the characteristics of the damper 13, such slip clutch caneffectively prevent excessive vibrations or oscillations of the units Aand B by destroying requisite amounts of surplus energy.

The characteristics (such as stiffness and/or the initial stress) of thecoil springs 52 can be readily seleceted in such a way that thesesprings perform a highly desirable shock absorbing action when the tooth27 of FIG. 2 approaches the tooth 29a or 29b. Such springs also preventthe tooth 27 from rebounding on impact against the tooth 29a or 28b,i.e., the springs 42 can be constructed and mounted to prevent directcontact between such teeth.

The slip clutch 14 can be used with particular advantage in motorvehicles wherein the space between the crankshaft 5 of the engine 105and the input element 10 of the change-speed transmission 110 is at apremium. This is due to the fact that the components 25, 29, thefriction generating elements 31, 31a occupy very little room, asconsidered in the axial direction of the flywheels 3 and 4.

As explained in connection with FIG. 3, the magnitude of nominal torquewhich the engine 105 transmits to the unit A can be less than themaximum torque (shown at 47) which can be transmitted by the damper 13.However, the maximum torque (46) which the slip clutch 14 can transmitis preferably a relatively small fraction (between 8 and 60 percent,most preferably between 10 and 35 percent) of nominal torque which theengine 105 transmits to the unit A.

The maximum torque (46) which the slip clutch 14 transmits between theflywheels 3 and 4 is preferably a small fraction (between 5 and 50percent and most preferably between 7 and 30 percent) of the maximumresistance (47) which the damper 13 can offer to rotation of the units Aand B with reference to each other. Such design of the slip clutch 14ensures that the assembly 1 can be constructed with a view to ensurethat only the damper 13 opposes rotation of the flywheel 3 relative tothe flywheel 4 (or vice versa) in a clockwise or counterclockwisedirection from a neutral position before the slip clutch becomesoperative (as at C during rotation in the direction of arrow 44 in FIG.3). The components 25 and 29 of the clutch 14 begin to slip relative toeach other when the torque of the already stressed (first and secondsets of) coil springs 38 of the damper 13 suffices to overcome theresistance of the means 31, 31a which oppose rotation of the components25 and 29 relative to each other. The coil springs 38 of the damper 13undergo additional stressing (as at D and E in FIG. 3) when thecomponents 25 and 29 can no longer turn relative to one another. Asalready explained in connection with FIG. 3, the situation is analogouswhen the flywheel 3 proceeds to turn in the direction of arrow 45 (afterhaving completed its angular movement in the direction of arrow 44 withreference to the flywheel 4), i.e., the coil springs 38 of the damper 13dissipate some energy before the components 25, 29 begin to turnrelative to each other and, when the angular movement of the components25, 29 relative to each other is completed, the springs 38 againdissipate energy (as at K).

In some instances, the slip torque of the clutch 14 can exceed thenominal torque of the engine 105.

It has been found that the slip clutch 14 will operate quitesatisfactorily if the components 25 and 29 can turn relative to eachother through angles of between 10 and 50 degrees, preferably between 15and 35 degrees. The angles of maximum angular displacement of thecomponents 25, 29 relative to each other an be between 60 and 110percent (preferably between 80 and 90 percent of the maximum angle ofangular displacement of the flywheels 3 and 4 relative to each other).Also, the maximum angle through which the components 25 and 29 can turnrelative to each other preferably exceeds the maximum angle throughwhich the flywheel 3 or 4 can turn clockwise or counterclockwise fromits starting or neutral position. As already mentioned above, the anglethrough which the flywheel 3 or 4 can turn in the direction of arrow 44(when the engine 105 drives the input element 10 of the change-speedtransmission 110) preferably exceeds the angle through which theflywheel 3 or 4 can turn in the direction of arrow 45 (coasting). Theslip clutch can more readily conform its operation to the vibrationcharacteristics of the engine 105 (i.e., of the prime mover) if at leasta portion (52) of the opposing means (31, 31a, 52) of the slip clutch isdesigned to start to oppose rotation of the units A and B relative toeach other after the flywheel 3 or 4 already completes a certain stageof its angular movement from the starting or neutral position. As alsomentioned above, the slip clutch is preferably a load-dependent clutchwhich comprises means (FIGS. 4-5) for offering frictional resistance ormeans (52) for storing energy only after the flywheel 3 or 4 has alreadycompleted a certain angular movement from the starting position.

FIGS. 4 and 5 illustrate a portion of a modified torsion dampingassembly wherein the components 125 and 129 of the slip clutch 114cooperate in a different way. The input component 125 of the clutch 114comprises a plate-like carrier 53 which axially movably supports severaldisc-shaped friction generating laminations or lamellae 54, 55 and 56.The radially outermost portions of the laminations 54, 55 and 56respectively carry radially extending teeth 54a, 55a and 56a received insockets or cutouts 53a provided in the inner edges face of theplate-like carrier 53 so as to prevent rotation of the laminations 54-56with reference to the input component 125.

The output components 129 of the slip clutch 114 also carries a set ofaxially shiftable laminations 57, 58, 59 which alternate with thelaminations 54, 55, and 56, as considered in the axial direction of theslip clutch 114. The radially innermost portions of the laminations 57,58 and 59 are respectively formed with teeth 57a, 58a, 59a which extendinto complementary sockets or cutouts 129a in the peripheral surface ofthe component 129.

The carrier 53 of the input component 125 further supports an annularwasher-lie stop 60 which is disposed at one side of the clutch 114(adjacent to the laminations 56 and 59). The other side of the carrier53 supports a group of radially extending leaf springs 61 which aresecured to the carrier 53 by rivets 62 and whose radially innermostportions bear upon the adjacent side of the lamination 54 so that theentire package of alternating laminations 54, 57, 55, 58, 56, 59 isurged axially against the stop 60 and the neighboring laminations areurged against each other. The rivets 62 preferably constitute the meansfor securing the stop 60 to the carrier 53 of the input component 125.The laminations 54 to 59 cooperate with each other, with the leafsprings 61 and with the stop 60 to oppose angular movements of thecomponents 125 and 129 of the slip clutch 114 relative to each other.

As can be seen in FIG. 4, the width of the teeth 57a, 58a, 59a on therespective laminations 57, 58, 59 (as considered in the circumferentialdirection of the components 125 and 129) is not uniform. Thus, each ofthe laminations 57, 58, 59 can turn with reference to the component 129to a different extent. This ensures that the friction generating means54-61 between the components 125 and 129 of the slip clutch 114 operatein several successive stages. In other words, the moment of frictionbetween the components 125 and 129 can vary in response to progressiveincrease of the angle through which the components 125 and 129 are movedangularly relative to each other.

FIG. 5 shows that the laminations 54 to 56 of the input components 125are in direct frictional engagement with the laminations 57, 58 and 59.However, it is equally possible to employ in the slip clutch 114 one ormore organic or inorganic friction rings which are interposed betweencertain laminations or between all of the neighboring laminations and/orbetween the lamination 54 and the leaf springs 61 to thereby influencethe friction between the components 125 and 129. In this manner, theslip clutch 114 can be caused to more accurately meet the specificationsin a particular type of torsion damping assembly.

The multi-stage slip clutch 114 of FIGS. 4 and 5 is especially suited toconform to the vibration characteristics of the engine and to thecharacteristics of the associated damper. As explained above, theresistance which the clutch 114 offers to rotation of the two unitsrelative to each other increases with increasing angular displacement ofthe components 125, 129 relative to each other.

FIGS. 6 and 7 illustrate a third slip clutch 214 with an input component225 and an output component 229. The latter comprises a disc-shapedmember 64 and a profiled member 63 which is made of sheet metal and issecured to the disc-shaped member 64 by rivets 163. The profiled member63 has a substantially Z-shaped cross-sectional outline and its radiallyoutermost portion 63b is integral with an axially extending annularportion 63a. The latter forms with the disc-shaped member 64 a troughfor a friction washer 65 which is adjacent to the inner side of themember 64 and is remote from the radially extending portion 63b. Theleft-hand side of the washer 65, as viewed in FIG. 6, is in contact withthe respective side of the input component 125. The space between theinput component 125 and the portion 63b of the profiled member 63 of theoutput component 129 accommodates a friction washer 66 which isnon-rotatably affixed to the component 125 as well as a washer 67 and afriction generating element 68 having prongs 68a extending in the axialdirection of the slip clutch 214 and into the adjacent cutouts 63b' ofthe portions 63b. A diaphragm spring 69 reacts against the inner side ofthe portion 63b and bears against the friction generating element 68.Thus, the diaphragm spring 69 urges the part 68 against the part 67which urges the part 66 and the component 225 against the part 65 sothat the latter is urged against the disc-shaped member 64 of the outputcomponent 229. The arms or prongs 68a of the friction generating element68 hold the latter against rotation with reference to the profiledmember 63, i.e., with reference to the output component 229.

As can be seen in FIG. 7, the washers 66 and 67 are formed with axiallyextending complementary male and female profiles or detent portions.Such detent portions form cam and follower means having ramps 70 and 71.Thus, and starting from the angular positions of the components 225, 229which are shown in FIG. 7, rotation of such components relative to oneanother in either direction from the neutral positions of FIG. 7 entailsan axial movement of the washers 66, 67 away from each other to therebychange the bias of the diaphragm spring 69 in dependency on the angularpositions of the components 225, 229 with reference to each other. This,in turn, entails a change in the slip torque of the clutch 214. The slptorque increase as the stress upon the diaphragm spring 69 increases. Inthe embodiment of FIGS. 6 and 7, the slip torque increases regardless ofwhether the washer 67 is rotated in a clockwise or in a counterclockwisedirection, as viewed in FIG. 7, because the cam and follower means whichis defined by the washers 66, 67 is shown in the neutral or medianposition. The slope of the ramp 70 can be different from that of theramp 71 so that the slip torque increases at a first rate then thewasher 66 or 67 is rotated in first direction and at a different secondrate when the washer 66 or 67 is rotated in a second direction counterto the first direction. The planes of the ramps 70, 71 are inclined withreference to a plane which is normal to the common axis of the flywheels(not shown in FIGS. 6 and 7).

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of our contributionto the art and, therefore, such adaptations should and are intended tobe comprehended within the meaning and range of equivalence of theappended claims.

We claim:
 1. An assembly for taking up and compensating for torque-induced shocks, especially for taking up and compensating for torque which is transmitted between an internal combustion engine and a change-speed transmission of a motor vheicle, comprising coaxial first and second units respectively comprising first and second flywheels and amounted for angular movements relative to each other, said first flywheel being connectable to an output element of the engine and said second flywheel being arranged to normally transmit torque to an input element of the transmission by way of a clutch; a damper disposed between said units and operative to yieldably resist angular movements of said units with reference to each other; and at least one slip clutch interposed between said units, operating in series with said damper and including opposing means for yieldably resisting a predetermined stage of angular movement of said units relative to each other.
 2. The assembly of claim 1, wherein said damper comprises a plurality of energy storing resilient elements acting in the circumferential direction of said units.
 3. The assembly of claim 1, wherein said damper comprises at least one friction generating device which is interposed between said units.
 4. The assembly of claim 1, wherein said slip clutch is a multi-stage slip clutch.
 5. The assembly of claim 1, wherein said slip clutch includes a plurality of stages each of which is arranged to offer a different resistance to rotation of said units relative to each other in different angular positions of such units with reference to one another.
 6. The assembly of claim 1, wherein said opposing means comprises resilient means.
 7. The assembly of claim 6, wherein said stage has first and second end portions and said resilient means is effective to oppose rotation of said units relative to each other in at least one end portion of said stage.
 8. The assembly of claim 1, wherein said damper includes an input component provided on one of said units and an output component non-rotatably secured to the other of said units.
 9. The assembly of claim 1, wherein said slip clutch are arranged to yieldably resist rotation of said flywheels relative to each other, said slip clutch comprising a first component extending substantially radially inwardly from one of said flywheels and a second component extending substantially radially outwardly from a portion of the other of said flywheels, one of said components having at least one tooth and the other of said components having a tooth space, said tooth extending into said tooth space with a predetermined clearance, as considered in the circumferential direction of said flywheels.
 10. The assembly of claim 9, wherein said one component is said first component and its tooth extends substantially radially inwardly of said one flywheel.
 11. The assembly of claim 9, wherein said opposing means comprises friction generating means interposed between said components to oppose angular movements of such components with reference to each other, as considered in the circumferential direction of said flywheels.
 12. The assembly of claim 11, wherein said friction generating means comprises at least one friction generating element non-rotatably affixed to one of said components and bearing against the other of said components.
 13. The assembly of claim 11, wherein said friction generating means comprises two friction generating elements non-rotatably affixed to one of said components, flanking the other of said components and bearing against such other component.
 14. The assembly of claim 9, wherein said opposing means comprises resilient means provided in said tooth space at least at one side of said tooth, as considered in the circumferentail direction of said flywheels.
 15. The assembly of claim 1, wherein said slip clutch further comprises an input component provided on one of said units and an output component on the other of said units, said opposing means comprising at least one lamination provided on one of said components, at least one lamination provided on the other of said components and means for biasing said laminations into frictional engagement with one another.
 16. The assembly of claim 1, wherein said slip clutch further comprises an input component provided on one of said units and an output component provided on the other of said units, said opposing means comprising at least one first lamination provided on one of said components, at least two second laminations flanking said first lamination, and means for biasing said second laminations into frictional engagement with said first lamination, said second laminations being mounted on and being rotatable with reference to said other component with different degrees of play, as considered inthe cirucmferential directin of said units.
 17. The assembly of claim 1, wherein said slip clutch further comprises an input component provided on one of said units and an output component provided on the other of said units, said opposing means comprising at least one first lamination provided on one of said components, at least second laminations provided on the other of said components and flanking said first lamination, and means for biasing said second lamination into frictional engagement with said first lamination, the friction between one of said second laminations and said first lamination being different from the friction between the other of said second laminations and said first lamination.
 18. The assembly of claim 1, wherein said slip clutch further comprises means for changing the resistance of said opposing emans to angular movements of said units relative to each other in response to changes in the angular positions of such units with reference to one another.
 19. The assembly of claim 18, wherein said opposing means comprises two neighboring friction generating elements and prestressed resilient means for biasing said friction generating element against each other, said means for changing the resistance of said opposing means comprising means for varying the stress upon said resilient means in response to angular movement of said units relative to each other.
 20. The assembly of claim 19, wherein said means for varying the stress upon said resilient means comprises cooperating am and follower means provided on said friction generating elements, one of said friction generating elements being arranged to share the angular movements of one of said units and the other of said friction generating elements being arranged to share the angular movements of the other of said units.
 21. The assembly of claim 20, wherein said resilient element comprises a diaphragm spring said cam and follower means comprises ramps which are inclined with reference to a plane extending at right angles to the common axis of said units.
 22. The assembly of claim 19, wherein said units are rotatable clockwise and counterclockwise relative to each other and said friction generating elements are movable by said units to predetermined neutral positions, siad means for changing the resistance of said opposing means being arranged to change such resistance in response to angular movement of at least one of said elements in either direction from said neutral position.
 23. The assembly of claim 1, wherein said first unit is arranged to receive from the engine torque of a predetermined magnitude and the magnitude or torque which said slip clutch can transmit is less than said predetermined magnitude.
 24. The assembly of claim 23, wherein the magnitude of torque which is transmitted by said slip clutch is between 8 and 60 percent of said predetermined magnitude.
 25. The assembly of claim 24, wherein the magnitude of torque which is transmitted by said slip clutch is between 10 and 35 percent of said predetermined magnitude.
 26. The assembly of claim 1, wherein said damper is arranged to transmit between said units a torque of predetermined magnitude and the magnitude or torque which is transmitted by said slip clutch is between 5 and 50 percent of said predetermined magnitude.
 27. The assembly of claim 26, wherein the magnitude of torque which is transmitted by said slip clutch is between 7 and 30 percent of said predetermined magnitude.
 28. The assembly of claim 1, wherein said first unit is arranged to receive from the engine nominal torque of a predetermined magnitude and the magnitude of torque which said damper is capable of transmitting between said units exceeds said predetermined magnitude.
 29. The assembly of claim 1, wherein said stage of angular movement is between 10 and 50 degrees.
 30. The assembly of claim 29, wherein said stage of angular movement is between 15 and 35 degrees.
 31. The assembly of claim 1, wherein said damper and said slip clutch are arranged to jointly permit an angular movement of said units through a predetermined angle with reference to each other and the slip clutch includes two components which are rotatable relative to each other through a second angle which is between 60 and 110 percent of said predetermined angle.
 32. The assembly of claim 31, wherein said second angle is between 80 and 90 percent of said predetermined angle.
 33. The assembly of claim 1, wherein said units are rotatable with reference to each other in clockwise and counterclockwise directions and said slip clutch further comprises first and second components which are respectively provided on said first and second units and are movable relative to each other against the resistance of said opposing means through an angle exceeding the maximum angle of clockwise or counterclockwise rotation of said units relative to each other.
 34. The assembly of claim 1, wherein said units are rotatable with reference to each other from a neutral position in clockwise and counterclockwise directions and the extent of angular movement of said units from neutral position in one of said directions exceeds the extent of angular movement in the other of said directions, said slip clutch being in series with said damper.
 35. The assembly of claim 1, wherein said units are movable relative to each other from a starting position in clockwise and counterclockwise directions and said opposing means includes means for resisting angular movements of said units relative to each other after such units complete a certain angular movement from said starting position in either of said directions.
 36. The assembly of claim 35, wherein said slip clutch is a load-responsive clutch and said opposing means is arranged to frictionally resist further rotation of said units relative to each other after said units complete said certain angular movement from said starting position.
 37. The assembly of claim 35, wherein said slip clutch is a load-responsive clutch and at least a portion of said opposing means is arranged to store energy and to thereby oppose further rotation of said units relative to each other after said units complete said certain angular movement from said starting position.
 38. The assembly of claim 1, wherein said first unit is arranged to receive from the engine nominal torque of a predetermined magnitude and the magnitude of torque whihch is transmitted by said slip clutch exceeds said predetermined magnitude. 